path: root/tools
diff options
authorYonghong Song <yhs@fb.com>2018-11-28 09:38:23 -0800
committerAlexei Starovoitov <ast@kernel.org>2018-11-28 16:40:02 -0800
commit528bff0cdb6649f97f2c4802e4ac7a4b50645f2f (patch)
tree057a93e4b227145b587f6b88598e814b0bf2e792 /tools
parentMerge branch 'btf-check-name' (diff)
tools: bpftool: fix a bitfield pretty print issue
Commit b12d6ec09730 ("bpf: btf: add btf print functionality") added btf pretty print functionality to bpftool. There is a problem though in printing a bitfield whose type has modifiers. For example, for a type like typedef int ___int; struct tmp_t { int a:3; ___int b:3; }; Suppose we have a map struct bpf_map_def SEC("maps") tmpmap = { .type = BPF_MAP_TYPE_HASH, .key_size = sizeof(__u32), .value_size = sizeof(struct tmp_t), .max_entries = 1, }; and the hash table is populated with one element with key 0 and value (.a = 1 and .b = 2). In BTF, the struct member "b" will have a type "typedef" which points to an int type. The current implementation does not pass the bit offset during transition from typedef to int type, hence incorrectly print the value as $ bpftool m d id 79 [{ "key": 0, "value": { "a": 0x1, "b": 0x1 } } ] This patch fixed the issue by carrying bit_offset along the type chain during bit_field print. The correct result can be printed as $ bpftool m d id 76 [{ "key": 0, "value": { "a": 0x1, "b": 0x2 } } ] The kernel pretty print is implemented correctly and does not have this issue. Fixes: b12d6ec09730 ("bpf: btf: add btf print functionality") Signed-off-by: Yonghong Song <yhs@fb.com> Acked-by: Song Liu <songliubraving@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'tools')
1 files changed, 3 insertions, 3 deletions
diff --git a/tools/bpf/bpftool/btf_dumper.c b/tools/bpf/bpftool/btf_dumper.c
index 55bc512a1831..e4e6e2b3fd84 100644
--- a/tools/bpf/bpftool/btf_dumper.c
+++ b/tools/bpf/bpftool/btf_dumper.c
@@ -32,7 +32,7 @@ static void btf_dumper_ptr(const void *data, json_writer_t *jw,
static int btf_dumper_modifier(const struct btf_dumper *d, __u32 type_id,
- const void *data)
+ __u8 bit_offset, const void *data)
int actual_type_id;
@@ -40,7 +40,7 @@ static int btf_dumper_modifier(const struct btf_dumper *d, __u32 type_id,
if (actual_type_id < 0)
return actual_type_id;
- return btf_dumper_do_type(d, actual_type_id, 0, data);
+ return btf_dumper_do_type(d, actual_type_id, bit_offset, data);
static void btf_dumper_enum(const void *data, json_writer_t *jw)
@@ -237,7 +237,7 @@ static int btf_dumper_do_type(const struct btf_dumper *d, __u32 type_id,
- return btf_dumper_modifier(d, type_id, data);
+ return btf_dumper_modifier(d, type_id, bit_offset, data);
jsonw_printf(d->jw, "(unsupported-kind");
return -EINVAL;